The present invention relates to a structured body of carbon having a protrusion of a specific form, which is electrically conductive and useful as a material of certain electronic parts such as cathode-ray tubes and as a measuring reference for a scanning probe microscope, as well as to a method for the preparation of such a structured body of carbon.
As is known, several novel structured bodies of carbon are highlighted in the material science of recent years including so-called fullerene compounds and carbon nanotubes. Molecules of a fullerene compound have a spherical closed-shell structure consisting of 60 carbon atoms or more which are bonded together forming a covalent bond each with the adjacent atoms to form a structure composed of a regular arrangement of carbon pentagons and carbon hexagons consisting carbon atoms only. A carbon nanotube, on the other hand, has a monolayered or multilayered structure which is a cylindrical closure of a graphite sheet having a diameter of 1 nm to several tens of nanometers.
It is a thought heretofore that the end portion of such a carbon nanotube and the surface of the fullerene molecule or a polyhedral carbon particle is provided with a frustum protrusion having a top flat of a structure of a carbon pentagon. This issue for the existence of such a structure has been a target of observations by using a transmission electron microscope although transmission electron microscopes are not suitable in principle to directly detect a frustum protrusion having a structure of the carbon pentagon because the images obtained thereby are limited to those obtained by the transmission of electrons. Namely, existence of such a frustum protrusion having a top flat of the structure of a carbon pentagon could not be directly detected. The subsequent development of a scanning tunneling microscope has afforded a possibility to directly observe the surface structure of a carbon body with a precision of an atomic level. The result obtained by the application of this technology, however, was contrary to the expectation and no frustum protrusions having a top flat of the structure of the carbon pentagon could be detected on the surface of the above mentioned structured bodies of carbon.
Fullerene compounds in general have a relatively low electric conductivity falling within the range of semiconductors so that they cannot be utilized as a good electron emitter. Apart from fullerene compounds, it could fairly be expected that carbon particles may have good electric conductivity and electron emissivity if the surface thereof is provided with a frustum protrusion having a top flat having a structure of a carbon pentagon to be useful as a material of certain electronic parts such as cathode-ray tubes and as a measuring reference for a scanning probe microscope by utilizing the feature of the protrusion of a sharp configuration in an atomic level.